What is Bell: Definition and 227 Discussions

A bell is a directly struck idiophone percussion instrument. Most bells have the shape of a hollow cup that when struck vibrates in a single strong strike tone, with its sides forming an efficient resonator. The strike may be made by an internal "clapper" or "uvula", an external hammer, or—in small bells—by a small loose sphere enclosed within the body of the bell (jingle bell).
Bells are usually cast from bell metal (a type of bronze) for its resonant properties, but can also be made from other hard materials. This depends on the function. Some small bells such as ornamental bells or cowbells can be made from cast or pressed metal, glass or ceramic, but large bells such as a church, clock and tower bells are normally cast from bell metal.
Bells intended to be heard over a wide area can range from a single bell hung in a turret or bell-gable, to a musical ensemble such as an English ring of bells, a carillon or a Russian zvon which are tuned to a common scale and installed in a bell tower. Many public or institutional buildings house bells, most commonly as clock bells to sound the hours and quarters.
Historically, bells have been associated with religious rites, and are still used to call communities together for religious services. Later, bells were made to commemorate important events or people and have been associated with the concepts of peace and freedom. The study of bells is called campanology.

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  1. I

    B Question about Bell's inequalities and 3-particle entanglement

    Could someone please clarify a question that I had? Is it true that 3 or more electrons/particles can be described under one wavefunction, making them entangled? If so, could you use Bell's principles of the comparison of their states like their spin, polarization or position to see if two out...
  2. M

    Can Bell's Inequality Be Proven Using Protons, Neutrons, or Other Particles?

    Hello I am MOHD HANZALA I worked on bell's inequality where we measure spin of electron along different basis leading to the bell's inequality . My question is that can we prove bell's inequality through proton or neutron or other particle??
  3. PeterDonis

    A Can We Construct a Coordinate Chart Where Bell Observers Are At Rest?

    A question that might occur to anyone reading about the Bell Spaceship Paradox is, can we construct a coordinate chart in which all of the Bell observers (i.e., observers following worldlines like those of the spaceships in the "paradox" scenario) are "at rest"? I put "at rest" in scare-quotes...
  4. L

    B Bell inequality test without polarisation?

    Was trying to understand the inequality test. The only article ever that I've found that explains it simply is the 1981 article, Bringing home the atomic world: Quantum Mysteries For Anybody. All other explanations require trust and understanding of polarisation, which is a huge deal. So i now...
  5. DrChinese

    A Can entanglement be detected in a single Bell pair?

    Can entanglement be detected in a single Bell pair? The canonical answer is NO, you can only see the entanglement in an ensemble of Bell pairs. For example, you could look at a stream of photon pairs coming from a PDC source. If you apply the CHSH formula (usually presented as an "S" value)...
  6. H

    I Global evolution of a Bell pair of photons

    Hi Pfs, consider a pair of maximally entangled photons where the total momentum is null and the same thing for the total angular momentum. I suppose that this pair is like an universe: nothing outside the pair acts on it except maybe a device for the measurement of these two properties (no local...
  7. G

    I Few Questions about: TU delft "A loophole-free Bell test"

    Electrons in diamonds are not entangled. Is above statement correct? Spin of emitted fotons if detected separately would not show any correlation? Is above statement correct? Is there assumption that spin of emitted fotons cannot change when reflecting or passing through beam spliter? Or...
  8. V

    I Contextuality, Complementarity, Signaling, and Bell tests

    See for the article https://www.mdpi.com/1099-4300/24/10/1380 This is a review devoted to the complementarity-contextuality interplay with connection to the Bell inequalities. Starting discussion with complementarity, we point out to contextuality as its seed. {\it Bohr-contextuality} is...
  9. V

    B Videos from Big Event 2015 (Växjö): Loophole free Bell test

    vhttps://play.lnu.se/media/t/0_hgz7034c A.Zeilinger: The Future of Bell Experiments. https://play.lnu.se/media/t/0_6jkhpefo G. Weihs: Violation of Bell’s Inequality under Strict Einstein Locality Conditions https://play.lnu.se/media/t/0_q2r30syq R. Hanson: From the first loophole-free Bell...
  10. .Scott

    B Is there another workable interpretation of the Bell Inequality?

    I just read an article in Quantum Magazine about "unitary" results and how this is tied to looking at the reversibility of quantum events. It provided an easy-to-understand mechanism for tracking the effects of adding information to a fictional universe. The example they gave for detecting a...
  11. M

    I Do Bell Experiments Show Local Overlap of Wave Functions Before Measurement?

    Consider experiments that demonstrate violations of Bell inequalities. I'm wondering about the spatial extent of the wave function of the particles BEFORE measurement. I assume the spatial extent is "very large," and my main question is whether they overlap. If the wave functions do overlap...
  12. bob012345

    If Ma Bell had not been Broken Up Would We have Smartphones Today?

    If Ma Bell had not been broken up would we have smartphones today?
  13. G

    I Why are terms like "deterministic" rarely used in Bell context

    Hi. In the context of Bell-like inequalities, the words to use seem to be "realism", "locality", "contextuality", "definiteness" and of course their negations. I have rarely seen those terms in classical physics (except maybe locality) before the Bell context. In classical physics (and...
  14. Killtech

    I Bell vs Kolmogorov: Unravelling Probability Theory Limits

    For some reason on this forums here I found some weird opinions that Bell's inequality were somehow disqualifying classical probability theory in general rather then showing merely the limits of locality. I do no understand where that misunderstanding comes from, so I decided to find out. Let's...
  15. Killtech

    I Weak measurement and the measurement problem

    When I think about it my biggest issue with the interpretation of QT can be boiled down to this question. There are the axioms of measurement in QT, which have their limiting nature and claim to be the only way to extract information from a quantum system - but that is just a claim with enough...
  16. plmustard

    B Bell Test Configuration Question

    Qutools makes quantum physics kits for educational purposes. Its quED kit is designed to help students learn about entanglement by performing Bell tests. In the manual section 5.1 it describes "the simplest test to verify entanglement of photon pairs." My question is if the entangled photons...
  17. microsansfil

    A Bell inequalities demonstration

    Hello, In this thesis https://tel.archives-ouvertes.fr/tel-01743877/document at "1.2.2 Bell inequalities" page 7-8 it's define a correlation function : C(x y) = P(+ + |x y) + P(− − |x y) − P(+ − |x y) − P(− + |x y), with −1 ≤ C(x y) ≤ 1. How do one get to this relationship −1 ≤ C(x y) ≤ 1 ...
  18. Demystifier

    A Assumptions of the Bell theorem

    Loosely speaking, the Bell theorem says that any theory making the same measurable predictions as QM must necessarily be "nonlocal" in the Bell sense. (Here Bell locality is different from other notions of locality such as signal locality or locality of the Lagrangian. By the Bell theorem, I...
  19. Cerenkov

    B The match rates in Bell Tests -- Lower than 50%?

    Hello. A friend and I are having a good-natured argument about tests of Bell's Theorem and he has directed me to this link. http://electron6.phys.utk.edu/phys250/modules/module 3/entangled_electrons.htm Our understanding of quantum physics should be considered as Basic. What we would like to...
  20. J

    Propeller with bell lift distribution has best thrust/power ratio?

    This source http://sustainableaviation.org/sas2017/session/prandtl-wing-maximum-efficiency/index.html claims : "Bell lift distribution can be applied to propulsion systems (no more “minimum induced loss”). We believe this results in a gain of 15.4% thrust for the same input torque/power." Bell...
  21. J

    I Exploring CV Bell State Measurement and Entanglement Swapping

    There is something I don't understand called CV Bell state measurement. In these two experiments they get two entangled beams "by overlapping phase-squeezed light with amplitude squeezed light with a phase difference of pi/2 at a 50-50 beamsplitter" See Figure 11...
  22. H

    I Bell measurement of distant particles

    Hi Pf I am looking at the figure in wiki about quantum teleportation. https://en.wikipedia.org/wiki/File:Quantum_teleportation_diagram.PNG A wants to send a qubit to B . She receives another qubit from a spdc. so she has to make a Bell measurement on them. Has these qbits to be close in space...
  23. J

    B Thought Experiment: Exploring Violations of Bell Inequalities

    I have been thinking about the Violation of bell inequalities , trying to justify how non locality can be determined from violation of bell tests. I have been through Dr. Chinese page which has partially convinced me that there can be no hidden variables , but I need to understand what...
  24. K

    I How do I compute the cumulative probabilites of multiple bell curves?

    I took statistics in university about two years ago, but I'm rusty. I was trying to write a zero player game - except sometimes, the player can control one of the characters, and I needed to be able to compute these probabilities. That said, I almost put this in homework help, but it is not...
  25. R

    B How to differentiate b/w two collapsed values in Bell States

    Given the Bell State in Z basis ##\psi = (a\uparrow \downarrow - b\downarrow \uparrow )## where ##a^2+b^2=1##. Now Alice has one particle and sends the other to Bob. Suppose Alice decides to measure her particle in Z direction. Thus entanglement collapses. Query: 1. How do we know which...
  26. Philip Koeck

    B Dangers with a diving bell combined with a long snorkel

    I'm thinking of using an upside down bucket placed at a depth of about 1 meter as a diving bell. Then I want to connect a garden hose pipe to a snorkel and put the other end of the hose pipe into the diving bell. I simply want more time and a bit of mobility under water in order to do a job. I...
  27. G Delta

    I Quantum Realism and Bell Locality

    I would like to pose a question (previously posed to DrChinese in a personal message) regarding Bell Locality. From PeterDonis in another thread: Bell assumes that local realism requires the factorizability of the joint probability function. Most of the efforts to justify this assumption have...
  28. M

    I Anton Zeilinger's comment about free will being required for science

    I'm not following the above quote about free will "This fundamental assumption is essential to doing science" If I perform experiments and find that conditions X are followed by conditions Y and Y=F(X) (or the probabilistic analog for QM), haven't I done science, independent of how much my free...
  29. Lynch101

    I Conflict between the Block Universe and Bell Tests?

    Usually questions I have of this nature are down to my limited understanding of the concepts, and this may be no different. Based on my understanding of the Block Universe interpretation of relativity, it appears to me as though there is a conflict between Bell tests and the Block Universe. To...
  30. K

    I The life cycle of a star and the bell shaped energy emission curve

    Do all stars in their life cycle (t) emit energy (E) that follow a bell shape curve? If yes, is the curve symmetrical always? How is this related to nuclear and thermal time scale?
  31. KeesDeVries

    I Photon Bell Experiment, what happens in a single case?

    I am wondering what happens in the case of 100 entangled photons with a polarization angle of 0 degrees (or 0 and 90) that interact with Alice at 22,5 degrees and Bob at 45 degrees in a Bell Experiment. Do I get a count of 85 for Alice and 50 for Bob, which means a maximum coincidence count...
  32. carter7gindenv

    I Why is the black body spectrum bell shaped if it's absorptance is equal to 1?

    This bother me too much. A black body is said to absorb every incoming radiation. Looking at absorptance we have : A=Φabs/Φreceived So if a Black body absorbs everything we have A=1 Φ is a flux meaning object/time. This means that whatever the wavelength a black body will absorb the maximal...
  33. R

    How to emulate the sound of a ringing bell?

    Summary: how to apply the the changes in frequency one can hear when a church bell is swinging through the air onto other acoustic sounds in a computer? Hello all, new to this forum. For an (art) sound installation I would like to apply the the changes in frequency one can hear when a church...
  34. G

    I Does EPR definitely rule out locality?

    Hi, Translated from German magazine "Spektrum der Wissenschaft", September 2009, p. 33 (original see below): That doesn't sound right. EPR even have "physical reality" in the title, though they might not mean with it the exact same thing as Bell. Why would we need Bell's argument if EPR...
  35. J

    B Help with Bell states and measurements

    Hi everyone! Sorry for the bad english! I'm trying to understand the "delayed choice entanglement swapping" (avaliable in https://arxiv.org/abs/1203.4834 ) and (long story short) , in the article we have pairs of photons that are entangled in the ## \phi \pm ## Bell state and the photons...
  36. Demystifier

    A Does the Bell theorem assume reality?

    A large portion of physicists thinks that Bell's theorem shows that reality does not exist. Another large portion of physicists thinks that reality is not an assumption of Bell's theorem, so that Bell's theorem just proves nonlocality, period. A third large portion of physicists thinks that both...
  37. nomadreid

    I Validity of a paper on the standard conclusions from Bell, etc

    In most popular explanations of entanglement, the quantum information of an entangled two-particle system changes without regard to the distance between the two particles. The following paper seems (to my unprofessional eye) to be questioning this interpretation...
  38. F

    B Franklin Bell: Does Positive/Negative Side Matter?

    hello all so i have been messing about with a homemade franklin bell. It is being charged with an electric fly swatter. I have been wondering if the neutral ball a the center should have any preference as to which side it would be attracted to FIRST. In my head i think it should not matter...
  39. corpsinhere

    I F(x, y) describing a distorted 3D Gaussian bell

    I am new to these forums - if I have posted in the wrong place please let me know. Standard 3D Gaussian bell: z = e^-(x^2) * e^-(y^2) From along the z-axis this looks "round". I would like a generalized f(x, y) which would look egg-shaped from above - possibly quite distorted.. I thought at...
  40. Islam Hassan

    Pressure on the Walls of a Rocket Motor Bell Nozzle

    Is the pressure due to the hot gas exhaust stream on the inside walls of a rocket motor bell nozzle positive or negative? Does the rocket exhaust exert a outward pressure on the nozzle walls due to the sheer volume of the exhaust gases or is the pressure a negative one due to the exhaust stream...
  41. DrChinese

    I Big Bell Test Collaboration: Challenging Local Realism with Human Choices

    Not sure if this reference has been posted yet, but I just saw it come through and thought I'd share. This is the "Big Bell Test Collaboration" using measurement choices provided by persons (as opposed to computer generated "random" choices). (The authors are a virtual who's who in the world...
  42. L

    I Generalizing the Bell Inequality for Arbitrary Measurement Axes

    EDIT: I realize now that I have fundamentally misunderstood a crucial aspect of deriving the Bell inequality for this case which is the existence of the third axis. The setup of the problem did state that the axes were chosen at random. Therefore I can't just look at the possibility of choosing...
  43. zonde

    I Do these Bell inequalities rely on probability concept?

    This question came up in another thread. I will post again the link to Nick Herbert's proof here: https://www.physicsforums.com/threads/a-simple-proof-of-bells-theorem.417173/#post-2817138 I don't see where the probability shows up in Nick Herbert's proof. For discussion of Eberhard's proof I...
  44. S

    How does an Electric Bell use the Motor Effect?

    I need help in explaining how electric bell uses motor effect.
  45. P

    I A computational model of Bell correlations

    I am no expert on the nuances of assumptions of various formulations of Bell theorem(s), but wonder if the following model is adequate to explain the correlations without any non-local features. If this is a known, flawed, approach, a pointer to its refutation (or an explanation) would be...
  46. H

    I Difference between CHSH and Bell inequalities

    Bell's Inequality, P(a,b)-P(a,d)+P(c,b)+P(c,d) is calculated as: S = a*b - a*d + c*b + c*d <= 2. It is valid for all values of a, b, c and d between -1 and +1 It is also valid for counts, a=a's counts/total counts of a,b,c &d. b, c,and d are derived similarly. Negative counts are not allowed...
  47. R

    I What are the physics behind a bell siphon in an aquaponics system?

    I'm trying to build a home aquaponics system, and a key component of the design I got off the internet is a bell siphon. So I'm trying to understand the physics of this siphon effect so I can optimize the weight and dimensions of the siphon to fit the size of my system.From what I read on the...
  48. H

    I Bell's Inequality is only valid for non-negative numbers

    The Bell Inequality tests are only valid for positive numbers, which is reasonable because counts and probabilities cannot be negative. CHSH generates a negative number, which means CHSH experiments are invalid. Bell's Inequality can be violated by having a negative value. For example...